Because Washington Democrats are constantly caucusing through June 21st
Washington state Democrats have only gone through the first round of caucuses, at the precinct level. The proportion of support for each candidate at this round of caucuses determines only the 34 delegates reported by the media, though the party leaders get to decide them at the state convention. Based on how people voted at the precinct level, the precincts will choose people to send to another caucus at the county and legislative district level, which chooses people to send to yet another caucus at the congressional district level, and to the state convention. The caucuses at the congressional district level then determines the other 67 delegates. Or they only determine 10 of the remaining 67 delegates and the state convention determines the rest. The state party's guide, which definitely contains some errors, is confusing on that point.
The Democratic Party in Washington has many rounds of caucuses and different kinds of delegates. The decisions for who become delegates and what proportion of different types of delegates are awarded to each candidate are distributed among the many rounds of caucuses.
The rounds are:
- Precinct-level Caucuses (the caucus that was conducted on March 26th)
- Legislative District Caucuses and County Conventions (different regions do one or the other, to be conducted on April 17th and May 1st, respectively)
- Congressional District Caucuses (to be conducted on May 21st)
- State Convention (to be conducted June 17th)
The types of delegates that get awarded to candidates are:
- At-large delegates (22)
- Pledged Party Leaders and Elected Officials (PLEOs) (12)
- Unpledged Party Leader and Elected Official Delegates (the super delegates) (17)
- Congressional District-Level Delegates (67)
The precinct-level caucuses determined how the state party leaders may apportion the at-large delegates and PLEOs to the candidates, but the party leaders won't do this until the state convention. That's where the numbers reported by the media comes from.
The precinct-level caucuses also sends people to the Legislative District Caucuses and County Conventions, which caucus and then choose people to send to the Congressional District Caucuses and to the State Convention.
Direct from the state party's guide where it starts to get confusing:
The congressional district caucuses will elect 58 delegates to the National Convention. Each congressional district caucus will also elect one presidential elector and one alternate.
The State Convention will elect presidential electors... In addition, those members of the Washington State Democratic Central Committee who represent Legislative Districts will ... elect 12 Pledged Party Leaders and Elected Official delegates (PLEOs), 19 delegates and 7 alternates to the National Convention.
You may also find a more satisfying answer somewhere here: